The present invention generally relates to a zone reflection type microwave oscillator using a dielectric resonator, and more particularly, to a construction of a DC cutting circuit to be in for the microwave oscillator.
Generally, referring to FIG. 3 which is a circuit diagram showing the essential portions of a conventional microwave oscillator of this type, a microstrip line 1 is connected between a transistor Tr of a bipolar type and a terminal resistor R. A dielectric resonator 2 is magnetically coupled with the strip line 1 to constitute a resonance circuit.
As a bipolar transistor Tr is used as a current driving type of negative resistance element in the microwave oscillator, it is necessary for a bias current to flow into the base of the bipolar transistor Tr. In order to prevent the bias current from flowing toward the terminal resistor R side, a chip capacitor C is connected between the microstrip line 1 and the terminal resistor R.
However, in the conventional microwave oscillator of the above-described construction, there is a problem in that the oscillation becomes unstable because of variations of the chip capacitor C itself, and the amount of the solder applied during the mounting operation of the chip capacitor C onto the basic plate.
Also, there is another problem in that the price of the microwave oscillator itself becomes higher, because a chip capacitor C as described hereinabove is expensive.